Extract fetching commit messages into injectable class

As other parts besides GerritHookFilter need to obtain commit
messages, we extract that method into an injectable class.

Change-Id: I40027347e1b8ef70b424ef056060465f08f2f404
2 files changed
tree: 12982dc0517545d0f95c3c55478bf6b7761f84e5
  1. .gitignore
  2. LICENSE
  3. hooks-its/
  4. pom.xml